In-coupling super grating, out-coupling super grating, image combiner and AR optical system

Abstract

The application provides a coupling-in superstructure grating, a coupling-out superstructure grating, an image combiner and an AR optical system, wherein the coupling-in superstructure grating comprises a plurality of coupling-in grating units arranged periodically; the coupling-in grating units are configured to emit a plurality of target light beams incident thereto at corresponding target diffraction orders, and the emission angles of different target light beams are the same; the different target light beams have different wavelengths, and the target diffraction orders are diffraction orders at which the corresponding target light beams are regulated and emitted by the coupling-in grating units. The coupling-in superstructure grating, the coupling-out superstructure grating, the image combiner and the AR optical system provided by the embodiments of the application can couple-in target light beams of different wavelengths at the same angle, for example, can couple-in target light beams of different wavelengths into an optical waveguide at the same angle, so that the coupled-in target light beams of different wavelengths can be uniformly propagated, and the rainbow effect can be effectively inhibited.

Description

Technical Field

[0001] This invention relates to the field of metagrating technology, and more specifically, to an input metagrating, an output metagrating, an image combiner, and an AR optical system. Background Technology

[0002] Diffractive waveguides can couple light beams into the waveguide using their included diffraction gratings, offering a wide range of applications. For example, they can be used in imaging scenarios such as AR (Augmented Reality) glasses. However, when diffractive waveguides are used for imaging, the diffraction gratings (such as surface relief gratings, SRGs) in the waveguide have different diffraction angles for light beams of different wavelengths (such as red, green, and blue RGB beams). Due to these different angles, after total internal reflection in the waveguide, the angles at which the light enters the coupling grating are also inconsistent. Therefore, different colors of light undergo different numbers of total internal reflections inside the waveguide, resulting in uneven proportions of the three colors (RGB) at different locations within the field of view, creating a rainbow effect.

[0003] Currently, the rainbow effect is mainly mitigated by designing multi-layer optical waveguides (e.g., three-layer optical waveguides) to process each color of RGB light separately; a schematic diagram of the three-layer optical waveguide structure can be found here. Figure 1 As shown. However, multilayer waveguides have the drawback of large size and weight, making them unsuitable for scenarios requiring thin and light waveguides, such as AR glasses. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide an input metagrating, an output metagrating, an image combiner, and an AR optical system.

[0005] In a first aspect, embodiments of the present invention provide a coupled meta-grating, comprising: a plurality of coupled grating units arranged periodically;

[0006] The coupling grating unit is configured to emit multiple incident target beams at corresponding target diffraction orders, and the different target beams have the same emission angle; the different target beams have different wavelengths, and the target diffraction order is the diffraction order of the corresponding target beam that is controlled by the coupling grating unit.

[0007] In one possible implementation, the coupling grating unit is configured to control multiple target beams incident at the same incident angle;

[0008] Different types of target beams correspond to different target diffraction orders.

[0009] In one possible implementation, the period length of the coupled grating unit is such that the wavelength of the target beam is inversely proportional to the corresponding target diffraction order.

[0010] In one possible implementation, the coupling grating unit is configured to control a variety of target beams incident at different incident angles.

[0011] In one possible implementation, the target diffraction order includes a first target diffraction order and a second target diffraction order;

[0012] The first exit angles corresponding to the first target diffraction order of different types of target beams are the same, and the second exit angles corresponding to the second target diffraction order of different types of target beams are the same.

[0013] The first emission angle and the second emission angle are biased toward different arrangement directions of the coupled grating units.

[0014] In one possible implementation, the coupling grating unit is configured to modulate multiple target beams that are vertically incident.

[0015] In one possible implementation, the multiple target beams include: a red band beam, a green band beam, and a blue band beam.

[0016] In one possible implementation, the coupled grating unit includes a plurality of coupled nanostructures arranged in a line along the shape of the coupled grating unit; at least some of the coupled nanostructures have different shapes.

[0017] In one possible implementation, the coupled nanostructure is a nanostructure determined by maximizing a minimum diffraction efficiency, which is the minimum diffraction efficiency among all the target beams.

[0018] In a second aspect, embodiments of the present invention also provide a coupling meta-grating, comprising: a plurality of coupling regions arranged sequentially along a preset direction, wherein the coupling regions include a plurality of coupling grating units arranged along the preset direction;

[0019] The coupling grating unit is configured to couple out multiple target beams incident at the same incident angle; the different target beams have different wavelengths;

[0020] The multiple target beams propagate along the preset direction as a whole, and the diffraction efficiency of the multiple coupling regions arranged sequentially along the preset direction gradually increases.

[0021] In one possible implementation, the diffraction efficiency of the coupled region satisfies:

[0022]

[0023] Where eff(n) represents the diffraction efficiency of the nth coupling region arranged along the preset direction, and N represents the total number of coupling regions.

[0024] In one possible implementation, the coupled grating unit includes a plurality of coupled nanostructures arranged in a line along the shape of the coupled grating unit; at least some of the coupled nanostructures have different shapes.

[0025] In one possible implementation, the coupled nanostructures in each of the coupled regions are determined by maximizing an objective function that satisfies:

[0026]

[0027] Among them, F i (n) represents the diffraction efficiency of the nth coupling region arranged along the preset direction for the i-th target beam. This represents the diffracted light intensity of the nth coupling region for the i-th target beam. Eff(n) represents the reflected light intensity of the nth coupling region to the i-th target beam, Eff(n) represents the theoretical diffraction efficiency corresponding to the nth coupling region, and N represents the total number of coupling regions.

[0028] Thirdly, embodiments of the present invention provide an image combiner, comprising: an input element, an optical waveguide, and an output element; the input element is located at the input end of the optical waveguide, and the output element is located at the output end of the optical waveguide;

[0029] The coupling element is a coupling meta-grating as described above, and / or the coupling element is a coupling meta-grating as described above;

[0030] The plurality of coupled-in meta-grating units in the coupled-in meta-grating are arranged along the overall propagation direction of the light beam, and the plurality of coupled-out meta-grating units in the coupled-out meta-grating are arranged along the overall propagation direction, which is the direction from the coupled-in end to the coupled-out end of the optical waveguide.

[0031] Fourthly, embodiments of the present invention provide an AR optical system, including an image combiner, an image source, and a relay lens group as described above;

[0032] The image source is located on the incident light side of the coupling element of the image combiner and is configured to incident an imaging beam containing at least three target beams onto the coupling element.

[0033] The relay lens group is located in the optical path of the image source and the image combiner, and is configured to project or magnify the target beam onto the image combiner at a 1:1 scale.

[0034] The solution provided in the first aspect of the present invention includes a plurality of periodically arranged coupling grating units. These coupling grating units regulate target beams of different wavelengths, controlling the target diffraction order corresponding to different target beams, thereby enabling different target beams to exit at the same exit angle after being incident on the coupling grating unit. This coupling meta-grating can couple target beams of different wavelengths at the same angle, for example, coupling target beams of different wavelengths into an optical waveguide at the same angle, allowing the coupled target beams of multiple wavelengths to propagate uniformly, effectively suppressing the rainbow effect. Furthermore, the coupling meta-grating is a single-layer structure, eliminating the need for multiple optical waveguides, resulting in a thin and lightweight structure suitable for applications such as AR glasses where size and weight are critical.

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A schematic diagram of an existing three-layer optical waveguide structure is shown.

[0038] Figure 2 This diagram shows a top view of a coupled meta-grating provided in an embodiment of the present invention.

[0039] Figure 3 This shows a schematic diagram of the first side view of the coupled meta-grating provided in an embodiment of the present invention;

[0040] Figure 4 This shows a schematic diagram of the second side view structure of the coupled meta-grating provided in an embodiment of the present invention;

[0041] Figure 5 This diagram shows a third side view of the coupled meta-grating structure provided in an embodiment of the present invention.

[0042] Figure 6 This shows a fourth side view of the coupled meta-grating structure provided in an embodiment of the present invention;

[0043] Figure 7 This shows a fifth side view of the coupled meta-grating structure provided in an embodiment of the present invention;

[0044] Figure 8 This diagram shows another top view of the coupled meta-grating provided in an embodiment of the present invention.

[0045] Figure 9 A top view schematic diagram of another coupled meta-grating provided in an embodiment of the present invention is shown;

[0046] Figure 10 This diagram shows a top view of a coupled meta-grating provided in an embodiment of the present invention.

[0047] Figure 11 This diagram shows a side view of a coupled meta-grating provided in an embodiment of the present invention.

[0048] Figure 12 A top view schematic diagram of another coupled meta-grating structure provided in an embodiment of the present invention is shown;

[0049] Figure 13 This diagram shows a side view of an image combiner provided in an embodiment of the present invention.

[0050] Figure 14 A schematic diagram of an AR glasses provided in an embodiment of the present invention is shown;

[0051] Figure 15 This diagram illustrates a structural schematic of a coupling grating unit provided in an embodiment of the present invention.

[0052] Figure 16 The far-field electromagnetic response diagram of the coupled metagrating provided in the embodiment of the present invention is shown;

[0053] Figure 17 This diagram illustrates a structural schematic of a coupling grating unit provided in an embodiment of the present invention.

[0054] Figure 18 The far-field electromagnetic response diagram of the coupled metagrating provided in the embodiment of the present invention is shown.

[0055] icon:

[0056] 10-Coupled grating unit, 101-Coupled nanostructure, 102-Substrate of coupled metagrating, 20-Coupled region, 21-Coupled grating unit, 211-Coupled nanostructure, 212-Substrate of coupled metagrating, 1-Coupled metagrating, 2-Coupled metagrating, 3-Optical waveguide, 4-Image source, 5-Relay mirror group. Detailed Implementation

[0057] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0058] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0059] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0060] This invention provides a coupled metagrating, which is a metagrating capable of achieving coupling functionality; see also Figure 2 As shown, the coupled metagrating includes a plurality of periodically arranged coupled grating units 10. The coupled grating units 10 are configured to emit incident target beams of various types at corresponding target diffraction orders, with different target beams having the same emission angle; different target beams have different wavelengths, and the target diffraction order is the diffraction order of the corresponding target beam controlled by the coupled grating units 10. For example, the metagrating can be designed to emit only light of a specific diffraction order, and the diffraction order specifically emitted by the metagrating is the target diffraction order.

[0061] In this embodiment of the invention, the coupled meta-grating includes multiple grating units, namely coupled grating units 10; and the multiple coupled grating units 10 are periodically arranged, for example, the multiple coupled grating units 10 can be periodically arranged along a certain preset direction. Figure 2 As shown, the strip-shaped coupling grating units 10 are arranged along a direction perpendicular to the x-direction, and multiple coupling grating units 10 are periodically arranged along the x-direction. Wherein, as... Figure 2As shown, multiple coupled grating units 10 can be arranged on the substrate 102 of the coupled metagrating, which can serve as a fixed support.

[0062] Furthermore, the coupled meta-grating can control the diffraction of multiple wavelengths of incident light beams. In this embodiment, the light beam incident on the coupled meta-grating is referred to as the target beam, and each target beam corresponds to a wavelength. Under the action of the coupled grating unit 10, the coupled meta-grating can control the diffraction effect on each target beam, so that each target beam can be emitted according to the diffraction order controlled by the coupled grating unit 10. In this embodiment, this diffraction order is referred to as the target diffraction order. By designing the diffraction effect of the coupled grating unit 10 on different types of target beams, it is possible to ensure that when each target beam is emitted according to the corresponding target diffraction order, the emission angle of different target beams is the same; for example, the target diffraction orders corresponding to different types of target beams are different, thereby enabling the coupled grating unit 10 to emit multiple target beams at the same emission angle.

[0063] For example, this coupled metagrating can be used for imaging, meaning that the incident light incident on the coupled metagrating includes at least: a red band beam, a green band beam, and a blue band beam. Figure 3 As shown, Figure 3 With L R L G L B These represent the red, green, and blue light beams, respectively; L represents the three light beams in red, green, and blue bands. R L G L B After being coupled into a meta-grating for diffraction, the target beams can exit at the same angle, meaning that the exit angles of the target beams in the three wavelength bands are the same. To illustrate that this coupled meta-grating can exit target beams of different wavelengths at the same angle, Figure 3 The red, green, and blue light beams are shown in an alternating pattern; those skilled in the art will understand that these beams may overlap or follow each other. Figures 4 to 7 Similar to this, it will not be elaborated further.

[0064] This invention provides a coupling meta-grating comprising a plurality of periodically arranged coupling grating units 10. Each coupling grating unit 10 modulates target beams of different wavelengths, controlling the target diffraction order corresponding to each beam, thereby ensuring that different target beams incident on the coupling grating unit 10 exit at the same exit angle. This coupling meta-grating can couple target beams of different wavelengths at the same angle, for example, coupling target beams of different wavelengths into an optical waveguide at the same angle, allowing the coupled target beams of multiple wavelengths to propagate uniformly and effectively suppressing the rainbow effect. Furthermore, this coupling meta-grating is a single-layer structure, eliminating the need for multiple optical waveguides, resulting in a thin and lightweight structure suitable for applications such as AR glasses where size and weight are critical.

[0065] Optionally, since the period length of the grating unit affects the relationship between the incident angle, exit angle, and diffraction order of the beam, embodiments of the present invention design a suitable period length so that the coupled metagrating can control the beam incident at a corresponding incident angle. For example, the general form of the metagrating can be expressed as (n out sinθ out -n inc sinθ inc ) / λ i =m i / p, λ i The wavelength corresponding to the metagrating, for example, the wavelength of the i-th target beam; n inc and n out The refractive indices of the external and metagratings, respectively, θ inc and θ out Let θ be the incident angle of the beam incident on the metagrating and the exit angle of the beam coupled to the metagrating. out θ represents the exit angle of the beam coupled into the optical waveguide by the metagrating; generally, θ out It needs to be greater than the critical angle for total internal reflection of the optical waveguide, m i The diffraction order is an integer, such as the target diffraction order corresponding to the wavelength of the i-th target beam; p is the period length of the grating unit. The period length p of the coupled grating unit 10 can be found in [reference needed]. Figure 2 As shown.

[0066] The coupled meta-grating allows multiple target beams to be incident at different incident angles. The coupled grating unit 10 of the coupled meta-grating is configured to control multiple target beams incident at different incident angles. When the incident angle of the target beam changes, its exit angle after being modulated by the coupled meta-grating also changes. By setting the incident angle of target beams of different wavelengths, it is easy to achieve the same exit angle for different target beams.

[0067] Optionally, at least some of the different target beams correspond to the same target diffraction order; for example, all target beams correspond to the same target diffraction order, such as all target beams having a target diffraction order of +2. In this embodiment of the invention, by setting a suitable period length p, and the incident angle, exit angle, etc. of different target beams, different target beams can be made to exit at the same exit angle; and at least some (e.g., all) of the different target beams correspond to the same target diffraction order, thereby enabling the simple and quick determination of parameters such as the period length of the coupled grating unit 10.

[0068] The incident light incident on the coupled metagrating includes a red-band beam L R Green band beam L G and blue band beam L B For example, see Figure 4 As shown, the coupled meta-grating 1 is located at the coupling end of the optical waveguide 3, and is used to couple three wavelength beams into the optical waveguide 3, so that the three wavelength beams can propagate along the optical waveguide 3. Figure 4 As shown, beams of three different wavelengths are incident on the coupled meta-grating 1 at different incident angles. Under the control of the coupled meta-grating 1, the beams of the three wavelengths all exit at the same exit angle θ. out It is coupled into optical waveguide 3. If the incident angles of the red, green, and blue light beams are θ respectively... R θ G θ B Then, based on the general form of the metagrating, we can obtain the following equation (1):

[0069]

[0070] Where, λ R , λ G , λ B These represent the wavelengths of the red, green, and blue light beams, respectively; for example, λ. R ≈720nm, λ G ≈540nm, λ B ≈432nm; m R m G m B The red, green, and blue target beams represent the target diffraction orders, respectively, and p represents the period length of the coupling grating unit 10. Furthermore, the three target diffraction orders can be the same, i.e., m... R =m G =m BBased on the above equation (1), it can be seen that there is a corresponding relationship between the incident angle and the period length. When the period length p is determined, the required incident angles of the three beams (red, green, and blue) can be easily calculated, so that the three beams (red, green, and blue) can be incident on the coupled meta-grating 1 at the corresponding incident angles, so that the coupled meta-grating 1 can couple out these beams at the same angle.

[0071] Alternatively, traditional diffraction gratings typically use the same diffraction order (usually +1 or -1). When beams of different wavelengths are incident on a traditional diffraction grating at the same angle, the different wavelengths have different diffraction angles for that diffraction order, i.e., different exit angles, resulting in a rainbow effect. In this embodiment of the invention, the coupling grating unit 10 can also achieve the emission of multiple target beams at the same exit angle by diffracting target beams of different wavelengths at different target diffraction orders. Specifically, the coupling grating unit 10 is configured to control multiple target beams incident at the same incident angle; and different target beams correspond to different target diffraction orders.

[0072] Based on the general form of a diffraction grating, when multiple target beams of different wavelengths are incident on the coupled meta-grating at the same incident angle, there is a one-to-one correspondence between the wavelength of the target beam and the target diffraction order. Since different target beams have different wavelengths, the target diffraction orders corresponding to different target beams are also different. Specifically, in this embodiment of the invention, by setting a suitable period length p for the coupled grating unit 10, under the constraint that the diffraction order is an integer, different target beams can be emitted at the same exit angle; at this time, the wavelength of the target beam and the corresponding target diffraction order are inversely proportional.

[0073] The incident light incident on the coupled metagrating includes a red-band beam L R Green band beam L G and blue band beam L B For example, see Figure 5 As shown, the coupled meta-grating 1 is located at the coupling end of the optical waveguide 3, and is used to couple three wavelength beams into the optical waveguide 3, so that the three wavelength beams can propagate along the optical waveguide 3. Figure 5 As shown, beams of three wavelengths are incident on coupled metagrating 1 at the same incident angle. If the incident angles of the red, green, and blue beams are θ respectively... R θ G θ B , then θ R =θ G =θ B Furthermore, under the control of the coupled metagrating 1, the beams in all three wavelength bands exit at the same exit angle θ. outIt is coupled into the optical waveguide 3. Based on the above equation (1), it can be seen that the wavelength of the target beam and the corresponding target diffraction order are inversely proportional, that is, the product of the wavelength of the target beam and the target diffraction order is a constant; for example, with θ inc The angle of incidence is θ. R =θ G =θ B =θ inc ,but:

[0074] (n out sinθ out -n inc sinθ inc p=λ i ×m i (2)

[0075] Where, λ i This represents the wavelength of the i-th type of target beam, for example, it can be λ. R , λ G , λ B ;m i This represents the target diffraction order corresponding to the i-th type of target beam.

[0076] Optionally, the coupled meta-grating can diffract a target beam according to two different diffraction orders, thereby diffracting the target beam to two different positions, so that the target beam coupled to the coupled meta-grating can be received at both positions. For example, the coupled meta-grating can achieve binocular imaging with a single image source. In this embodiment of the invention, for any target beam, its target diffraction order includes a first target diffraction order and a second target diffraction order. Furthermore, the first exit angle corresponding to the first target diffraction order of different target beams is the same, and the second exit angle corresponding to the second target diffraction order of different target beams is the same; the first exit angle and the second exit angle are biased towards different arrangement directions of the coupled grating unit 10.

[0077] In this embodiment of the invention, the coupled meta-grating can diffract a portion of the target beam according to a first target diffraction order, with its exit angle being a first exit angle; the coupled meta-grating can also diffract another portion of the target beam according to a second target diffraction order, with its exit angle being a second exit angle. Furthermore, all target beams have the same first exit angle and all target beams have the same second exit angle.

[0078] The first exit angle is different from the second exit angle, meaning that all target beams can be directed to two different positions in an overlapping manner. Furthermore, the first and second exit angles are biased towards different arrangement directions of the coupling grating units 10. In this embodiment of the invention, the coupling grating units 10 are periodically arranged, and this arrangement essentially corresponds to two arrangement directions; accordingly, the coupling grating units 10 bias the target beams towards different arrangement directions, that is, the two exit angles (the first exit angle and the second exit angle) of the target beams are biased towards different arrangement directions. For example, as... Figure 2 and Figure 6 As shown, the plurality of coupling grating units 10 are arranged along the x-direction (or, the +x-direction), and the plurality of coupling grating units 10 are also arranged along the opposite direction to the x-direction (or, the -x-direction); accordingly, see Figure 6 As shown, the coupling grating unit 10 emits a portion of the target beam at a first emission angle θ1, which is biased towards the +x direction; the coupling grating unit 10 emits another portion of the target beam at a second emission angle θ2, which is biased towards the -x direction, so that the target beam can be transmitted to both sides of the coupling meta-grating respectively, thereby enabling binocular imaging in the case of a single image source.

[0079] Optionally, see Figure 7 As shown, the coupling grating unit 10 is configured to control multiple target beams incident perpendicularly. At this time, for a certain target beam, the diffraction order of the coupling grating unit 10 for that target beam has a positive and negative relationship; for example, the first target diffraction order is +m, and the second target diffraction order is -m.

[0080] Based on any of the above embodiments, see Figure 8 As shown, the coupling grating unit 10 includes a plurality of coupling nanostructures 101 arranged in a line along the shape of the coupling grating unit 10; and at least some of the coupling nanostructures 101 have different shapes; wherein, Figure 8 All coupled nanostructures 101 in the figure are represented by circles, and different shapes of coupled nanostructures 101 are not shown.

[0081] The coupling grating unit 10 is generally a strip-shaped structure, and includes multiple coupling nanostructures 101, which are arranged in a line along the shape of the coupling grating unit 10. Figure 8As shown, the coupling grating unit 10 is a strip structure perpendicular to the x-direction, and correspondingly, multiple coupling nanostructures 101 are arranged in a line along the x-direction. Optionally, the coupling grating unit 10 may only include multiple coupling nanostructures 101, that is, multiple coupling nanostructures 101 constitute the coupling grating unit 10, and multiple coupling nanostructures 101 arranged in a line form a strip structure coupling grating unit 10.

[0082] In this embodiment of the invention, all coupled grating units 10 are identical, but at least some coupled nanostructures 101 within the coupled grating unit 10 have different shapes. For example, all coupled nanostructures 101 in the coupled grating unit 10 have different shapes. Optionally, the shape of the coupled nanostructure 101 is polarization-insensitive. For example, the coupled nanostructure 101 has two orthogonal planes of symmetry, and each part of the coupled nanostructure 101 divided by these two planes of symmetry is identical; for example, the coupled nanostructure 101 has an axis of symmetry, and its shape remains unchanged when rotated 90° along the axis of symmetry. For example, the shape of the coupled nanostructure 101 includes at least one of the following: cylindrical, annular, square annular, and cross-shaped.

[0083] Among them, such as Figure 8 As shown, the coupled meta-grating may consist of only one row of coupled grating units 10; or, as... Figure 9 As shown, the coupled meta-grating may also include multiple rows of coupled grating units 10, each row of coupled grating units 10 being arranged along the x-direction.

[0084] To enable the coupling grating unit 10 to emit target beams of different wavelengths according to a specific diffraction order (i.e., the target diffraction order), simply designing the parameters of the coupling grating unit 10 (e.g., the period length p of the coupling grating unit 10) is insufficient to ensure that light of different wavelengths is emitted according to the corresponding target diffraction order. This can easily lead to the coupling metagrating failing to achieve the required function; for example, this may result in the coupling metagrating having low diffraction efficiency for a certain wavelength. Optionally, in this embodiment of the invention, the coupling grating unit 10 is designed with nanostructures of different shapes (i.e., coupling nanostructure 101). This introduces the design freedom of the nanostructure shape, giving the coupling grating unit 10 more possibilities. This allows for the design of a coupling grating unit 10 that meets the required requirements, meaning that the coupling grating unit 10 can effectively emit target beams of different wavelengths at the same emission angle.

[0085] Optionally, when designing the coupling grating unit 10, diffraction efficiency can be the target, so that the final coupling grating unit 10 can emit any target beam with a relatively high diffraction efficiency. Specifically, the coupling nanostructure 101 is a nanostructure determined by maximizing the minimum diffraction efficiency, which is the minimum value among the diffraction efficiencies of all target beams.

[0086] In this embodiment of the invention, during the design of the coupling grating unit 10, multiple nanostructures with at least some different shapes can be formed into candidate grating units, and the diffraction efficiency of the candidate grating unit for each target beam can be determined. For example, the electric field intensity of a target beam passing through a metagrating composed of candidate grating units can be decomposed into plane waves with different Fourier orders, thereby determining the electric field intensity of the target diffraction order of the target beam, and the diffraction efficiency of the candidate grating unit for the target beam can be represented by the electric field intensity. This embodiment of the invention determines the minimum diffraction efficiency among all target beams, i.e., the minimum diffraction efficiency, and uses this minimum diffraction efficiency as an optimization target. By maximizing this minimum diffraction efficiency, a candidate grating unit with a relatively large minimum diffraction efficiency can be obtained, which can then be used as the required coupling grating unit 10. For example, the coupling grating unit 10 needs to control target beams in three bands: red, green, and blue, and the diffraction efficiencies of each target beam are: F... R F G F B Then the optimization objective F can be expressed as F = min(F R ,F G ,F B By maximizing the optimization objective F, the desired coupling grating unit 10 can be designed, which has a high diffraction efficiency.

[0087] The coupling meta-grating provided in the above embodiments of the present invention can couple multiple wavelengths of target beams at the same exit angle, that is, the multiple wavelengths of target beams coupled in can overlap; correspondingly, the embodiments of the present invention also provide a coupling meta-grating, which can couple multiple wavelengths of target beams incident at the same angle. For example, the coupling meta-grating can couple multiple wavelengths of target beams coupled in by the coupling meta-grating.

[0088] Specifically, see Figure 10As shown, the coupling meta-grating includes a plurality of coupling regions 20 arranged sequentially along a preset direction, and each coupling region 20 includes a plurality of coupling grating units 21 arranged along the preset direction. The coupling grating units 21 are configured to couple out multiple target beams incident at the same incident angle; different target beams have different wavelengths; the multiple target beams propagate as a whole along the preset direction, and the diffraction efficiency of the plurality of coupling regions 20 arranged sequentially along the preset direction gradually increases. Wherein, as... Figure 10 Multiple coupled grating units 21 can be arranged on a substrate 212 of the coupled metagrating, which serves as a fixed support.

[0089] like Figure 10 As shown, the x-direction represents the preset direction, and multiple coupling regions 20 are arranged sequentially along the x-direction; and each coupling region 20 contains multiple grating units, namely coupling grating units 21, and the multiple coupling grating units 21 are also arranged along the x-direction. Figure 10 The example shown is an coupled metagrating comprising three coupled regions 20, and each coupled region 20 includes three coupled grating units 21. Those skilled in the art will understand that the coupled region 20 is a portion of the coupled metagrating, but this does not mean that multiple coupled regions 20 need to be divided; that is, the coupled metagrating remains a monolithic structure. For example, as... Figure 10 As shown, the coupled meta-grating contains nine coupled grating units 21, which can be divided into three parts along the x-direction, each part corresponding to a coupled region 20.

[0090] The coupling meta-grating is used to couple out target beams of multiple wavelengths propagating along the x-direction, with each target beam incident on the grating at the same angle of incidence; wherein, in the x-direction, the diffraction efficiency of the coupling region 20 gradually increases. The target beams propagate along the x-direction. Figure 10 The diffraction propagates in the x-direction, meaning it propagates from left to right overall; and the diffraction efficiency of the coupling region 20 gradually increases. Figure 10 The leftmost coupling region 20 has the lowest diffraction efficiency, the middle coupling region 20 has a relatively high diffraction efficiency, and the rightmost coupling region 20 has the highest diffraction efficiency.

[0091] In this embodiment of the invention, the coupling metastructure grating is used to couple out a light beam, typically for coupling out a light beam propagating along an optical waveguide. For example... Figure 11 As shown, the optical waveguide 3 is arranged along the x-direction, and target beams of various wavelengths can propagate along the optical waveguide 3 under the reflection (e.g., total internal reflection) effect of the optical waveguide 3, so that the target beam propagates entirely along the x-direction. Furthermore, a coupling meta-grating 2 is disposed at the coupling end of the optical waveguide 3, and the coupling grating units 21 in the coupling meta-grating 2 are arranged along the x-direction; and... Figure 11 The boundary between two adjacent coupling regions 20 is represented by dashed lines, and different gray levels represent the coupling grating units 21 in different coupling regions 20. A beam A (which contains beams of multiple wavelengths) propagating along the optical waveguide 3 can first be incident on the leftmost coupling region 20 of the coupling meta-grating. Since the diffraction efficiency of this coupling region 20 is the lowest, a small part of the beam A can be coupled out, that is, the beam A1 is coupled out, and the rest can continue to propagate along the optical waveguide 3, that is, the beam B continues to propagate along the optical waveguide 3. The light beam B can be incident on the middle coupling region 20 of the coupling meta-grating. Although the intensity of beam B is lower than that of beam A (because part of beam A1 in beam A is coupled out), the middle coupling region 20 has a higher diffraction efficiency. Therefore, this coupling region can still couple out a suitable amount of beam B1. The remaining beam C (i.e., the remaining part of beam B) can continue to propagate along the optical waveguide 3 and be incident on the rightmost coupling region 20. Since the rightmost coupling region 20 has the highest diffraction efficiency, it can still couple out a suitable amount of beam C1. For example, if the diffraction efficiency of the rightmost coupling region 20 is 1, it can couple out all beams. This embodiment of the invention utilizes multiple coupling regions 20 with gradually increasing diffraction efficiency to uniformly couple out target beams of various wavelengths, resulting in a relatively uniform intensity distribution on the output side of the coupling meta-grating.

[0092] Optionally, the diffraction efficiency of the coupling region 20 satisfies:

[0093]

[0094] Where eff(n) represents the diffraction efficiency of the nth coupling region 20 arranged along the preset direction, and N represents the total number of coupling regions 20.

[0095] In this embodiment of the invention, n represents the sequence number of the coupling regions 20 arranged along a preset direction. Based on the above formula (3), the diffraction efficiency of each coupling region 20 can be determined. For example, as Figure 11 As shown, the coupled meta-grating includes three coupled regions 20, i.e., N=3; correspondingly, Figure 11 The three coupling regions 20, numbered 1, 2, and 3 from left to right, have diffraction efficiencies of 1 / 3, 1 / 2, and 1, respectively. In this case, the light intensity of the beams coupled out of each coupling region 20 is basically the same, that is, the light intensities of beams A1, B1, and C1 are basically the same; without considering losses, the light intensities of beams A1, B1, and C1 are all one-third of the light intensity of the incident beam A.

[0096] It should be noted that the diffraction efficiency eff(n) refers to the actual diffraction efficiency of the nth coupling region 20. Due to process limitations and the difficulty in determining a fully compliant coupling grating unit 21, the actual diffraction efficiency eff(n) of the nth coupling region 20 is unlikely to completely satisfy the above formula (3). In this embodiment of the invention, within the allowable error range, as long as the diffraction efficiency eff(n) of the nth coupling region 20 is consistent with the above formula (3), the actual diffraction efficiency eff(n) of the nth coupling region 20 is consistent with the above formula (3). The difference is not significant, for example, At this point, it can be assumed that the diffraction efficiency of the nth coupling region 20 satisfies the above equation (3).

[0097] Based on any of the above embodiments, see Figure 12 As shown, the coupling grating unit 21 includes a plurality of coupling nanostructures 211 arranged in a line along the shape of the coupling grating unit 21; and at least some of the coupling nanostructures 211 have different shapes; wherein, Figure 12 Different shapes of the coupled nanostructure 211 are not shown.

[0098] Similar to the coupling-in grating unit 10, the coupling-out grating unit 21 has an overall strip-shaped structure. The coupling-out grating unit 21 includes multiple coupling-out nanostructures 211, and these nanostructures 211 are arranged in a line along the shape of the coupling-out grating unit 21. For example... Figure 12 As shown, the coupling grating unit 21 is a strip structure perpendicular to the x-direction, and correspondingly, multiple coupling nanostructures 211 are arranged in a line perpendicular to the x-direction. Optionally, the coupling grating unit 21 may only include multiple coupling nanostructures 211, that is, multiple coupling nanostructures 211 constitute the coupling grating unit 21, and multiple coupling nanostructures 211 arranged in a line form a strip structure coupling grating unit 21.

[0099] In this embodiment of the invention, all coupling grating units 21 within a coupling region 20 are identical, but at least some of the coupling nanostructures 211 within the coupling grating unit 21 have different shapes. For example, all coupling nanostructures 211 within the coupling grating unit 21 have different shapes. Optionally, the shape of the coupling nanostructure 211 is a polarization-insensitive shape. For example, the coupling nanostructure 211 has two orthogonal planes of symmetry, and each part of the coupling nanostructure 211 divided by these two planes of symmetry is completely identical; for example, the coupling nanostructure 211 has an axis of symmetry, and its shape remains unchanged when rotated 90° along the axis of symmetry. For example, the shape of the coupling nanostructure 211 includes at least one of the following: cylindrical, annular, square annular, and cross-shaped.

[0100] Optionally, as described above, the diffraction efficiencies of the coupling grating units 21 in different coupling regions 20 for the target beam are different, but the diffraction efficiency of a coupling region 20 for target beams of different wavelengths should be the same; in addition, the coupling grating unit 21 can also be configured to emit multiple target beams incident at the same incident angle at the same exit angle; that is, the coupling grating unit 21 also controls the diffraction order for target beams of different wavelengths. In order to enable the coupling grating unit 21 to emit target beams of different wavelengths with a specific diffraction efficiency, simply designing the parameters of the coupling grating unit 21 (e.g., the period length of the coupling grating unit 21) can easily lead to the coupling meta-grating failing to achieve the required function; for example, this may cause some coupling regions 20 to have a diffraction efficiency that does not meet the requirements for a certain wavelength. Optionally, in this embodiment of the invention, the coupling grating unit 21 is designed with nanostructures of different shapes (i.e., coupling nanostructure 211), which can introduce the design freedom of nanostructure shape, making the coupling grating unit 21 more possible, thereby enabling the design of a coupling grating unit 21 that meets the required requirements, that is, the coupling grating unit 21 can diffract target beams of multiple wavelengths according to the required diffraction efficiency.

[0101] Optionally, to ensure that the diffraction efficiency of each coupling region 20 meets the required requirements, such as satisfying the above equation (3), this embodiment of the invention sets an objective function. By maximizing this objective function, the coupling nanostructure 211 is optimized, thereby determining the coupling nanostructure 211 that enables the diffraction efficiency of the corresponding coupling region 20 to meet the required requirements. The objective function satisfies:

[0102]

[0103] Among them, F i (n) represents the diffraction efficiency of the nth coupling region 20 arranged along the preset direction for the i-th type of target beam. This represents the diffracted light intensity of the 20 pairs of the i-th target beam in the n-th coupling region. Eff(n) represents the reflected light intensity of the nth coupling region 20 to the i-th target beam, Eff(n) represents the theoretical diffraction efficiency corresponding to the nth coupling region 20, that is, the diffraction efficiency that the nth coupling region 20 should have, and N represents the total number of coupling regions 20.

[0104] In this embodiment of the invention, for the nth coupling region 20, the higher its theoretical diffraction efficiency Eff(n), the higher the corresponding diffraction intensity. The larger the intensity, the better. For the last coupling region 20, i.e., n=N, directly measure its diffracted light intensity. The optimization objective is to make the actual diffraction efficiency eff(n) of the last coupled region 20 close to 1. For other coupled regions 20, as shown in equation (4) above, the difference between the theoretical diffraction efficiency Eff(n) and the current actual diffraction efficiency eff(n) is determined based on their ideal theoretical diffraction efficiency Eff(n). In this embodiment, the difference is... and The smaller value in the equation represents the difference between the two. The larger this smaller value is, the closer the current actual diffraction efficiency eff(n) is to the theoretical diffraction efficiency Eff(n). By maximizing this minimum value (i.e., maximizing F...), the desired effect can be achieved. i (n)) can make the actual diffraction efficiency eff(n) of the finally determined nth coupling region 20 consistent with the theoretical diffraction efficiency Eff(n).

[0105] The theoretical diffraction efficiency Eff(n) can be predetermined. For example, a coupled metagrating contains three coupled regions 20, i.e., N=3. The theoretical diffraction efficiencies Eff(n) of the three coupled regions 20 should be 1 / 3, 1 / 2, and 1, respectively. Those skilled in the art will understand that Eff(n) represents the ideal diffraction efficiency of the nth coupled region 20, which may deviate slightly from the actual diffraction efficiency eff(n) of the nth coupled region 20. Ideally, eff(n) = Eff(n).

[0106] This invention provides a coupling meta-grating comprising multiple coupling regions 20 arranged along a preset direction, with the diffraction efficiency of the coupling regions 20 increasing sequentially. When a target beam propagating along the preset direction is incident on the coupling meta-grating, it can be uniformly coupled out by the multiple coupling regions 20, achieving pupil replication and increasing the eyebox range. Furthermore, by optimizing the nanostructure according to the above-mentioned optimization objectives, the required coupling nanostructure 211 for each coupling region 20 can be determined, ensuring that the diffraction efficiency of each coupling region 20 meets the required requirements.

[0107] Optionally, embodiments of the present invention also provide an image combiner, see below. Figure 13 As shown, the image combiner includes: an input element, an optical waveguide 3, and an output element; the input element is located at the input end of the optical waveguide, and the output element is located at the output end of the optical waveguide. The input element is the input meta-grating 1 provided in any of the above embodiments, and / or the output element is the output meta-grating 2 provided in any of the above embodiments. Figure 13As shown, the coupled meta-grating 1 is located at the coupled end of the optical waveguide, and the coupled extrusion meta-grating 2 is located at the coupled end of the optical waveguide. The plurality of coupled grating units 10 in the coupled meta-grating 1 are arranged along the overall propagation direction of the light beam, and the plurality of coupled extrusion grating units 21 in the coupled extrusion meta-grating 2 are also arranged along this overall propagation direction, which is the direction from the coupled end to the coupled end of the optical waveguide 3.

[0108] In this embodiment of the invention, the plurality of coupled-in grating units 10 in the coupled-in metagrating 1 and the plurality of coupled-out grating units 21 in the coupled-out metagrating 2 are arranged along the overall propagation direction of the light beam within the optical waveguide 3, that is, along the setting direction of the optical waveguide 3. Figure 13 As shown, the coupling end of optical waveguide 3 is located on its lower left surface, and the coupling end of optical waveguide 3 is located on its lower right surface. The light beam can propagate entirely from left to right within optical waveguide 3, that is, along... Figure 13 The beams propagate in the x-direction; correspondingly, the coupled-in grating unit 10 and the coupled-out grating unit 21 are both arranged along the x-direction. Under the action of the coupled-in meta-grating 1, target beams of multiple wavelengths can propagate in the optical waveguide 3 at the same angle, which can effectively suppress the rainbow effect; and at the coupled-out end, target beams of multiple wavelengths can be uniformly coupled out by the coupled-out meta-grating 2, which can realize pupil replication, increase the eye movement range, and improve the visual comfort of the human eye.

[0109] Optionally, embodiments of the present invention also provide an AR optical system, which includes an image combiner and an image source 4 as described above, such as... Figure 13 The image source 4 is shown; located on the incident light side of the coupling element, the image source 4 is configured to incident an imaging beam containing at least three target beams onto the coupling element. For example, the image source 4 can emit an imaging beam containing red, green, and blue wavelengths and direct the imaging beam toward the coupling meta-grating 1; the coupling meta-grating 1 couples the imaging beam into the optical waveguide 3 and propagates along the optical waveguide 3, and finally the imaging beam is coupled out by the coupling out meta-grating 2. An observer located at the coupling out meta-grating 2 can then view the image formed by the image source 4.

[0110] Furthermore, the AR optical system also includes a relay lens group 5, located in the optical path between the image source 4 and the image combiner, configured to project or magnify the target beam onto the image combiner. For example... Figure 14 As shown, image source 4 is located at the temple of the AR glasses, and the imaging light emitted from image source 4 is incident on the coupling element through relay lens group 5. Figure 14 The coupling element is not shown. Furthermore, the lens (or part of the lens) of the AR glasses can act as an optical waveguide 3 and propagate the imaging light; finally, the imaging light is coupled out by the coupling element and directed towards the human eye.

[0111] The structure and function of the image combiner are described in detail below through an embodiment.

[0112] In this embodiment of the invention, a schematic diagram of the image combiner can be found here. Figure 13 As shown. The light emitted from image source 4 is RGB tri-color light, that is, a beam containing red, green, and blue wavelengths. This RGB beam is modulated by the coupling meta-grating 1, incident into the optical waveguide 3 at a total internal reflection angle, and undergoes total internal reflection within the optical waveguide 3. Finally, it is coupled out to the human eye by the coupling meta-grating 2. The basic structure of the coupling meta-grating 1 can be found in [reference needed]. Figure 8 or Figure 9 As shown, the basic structure of the coupled metagrating 2 can be found in [reference needed]. Figure 12 As shown.

[0113] In this embodiment of the invention, the coupled meta-grating 1 has dimensions of 10mm × 10mm, the optical waveguide 3 has a thickness of 4mm and a width of 10mm, and its length can be determined according to actual conditions, such as the size of eyeglasses, and is usually around 20mm. The coupled meta-grating 1 includes tens of millions of coupled nanostructures 101, wherein every 8 coupled nanostructures 101 form a coupled grating unit 10, that is, each coupled grating unit 10 corresponds to 8 coupled nanostructures 101. The shapes of these 8 coupled nanostructures 101 are all different. Figure 15 A top view of a coupled grating unit 10 is shown; the specific shapes of the eight coupled nanostructures 101 can be found in [reference needed]. Figure 15 As shown. Figure 15 As shown, each coupled nanostructure 101 is insensitive to polarization; the dimensions of the eight coupled nanostructures 101 are shown in Table 1 below.

[0114] Table 1

[0115]

[0116] In Table 1, dimension 1 represents the outer dimension of the coupled nanostructure 101, such as half of the outer radius or outer side length of the coupled nanostructure 101; dimension 2 represents the inner dimension of the coupled nanostructure 101, such as half of the inner radius or inner side length of the coupled nanostructure 101. The units for dimensions 1 and 2 are both nm. For a cross-shaped columnar coupled nanostructure 101 (such as...), ... Figure 15 The 7th nanostructure in the design has a dimension 1 representing half the length of the cross shape, and a dimension 2 representing half the width of each protruding part of the cross shape. This dimension 2 is also half the side length of the square at the center of the cross. The far-field electromagnetic response of this coupled metagrating 1 can be found in [reference needed]. Figure 16 As shown; where, Figure 16 The horizontal axis represents the sine value of the far-field refraction angle, and the vertical axis represents the wavelength.

[0117] Furthermore, the dimensions of the coupled metagrating 2 are 10mm × 10mm. Each coupled grating unit 21 in the coupled metagrating 2 comprises 5 coupled nanostructures 211; wherein, the shapes of these 5 coupled nanostructures 211 are different from each other. Figure 17 A top view of a coupling grating unit 21 is shown; the specific shapes of the five coupling nanostructures 211 can be found in [reference needed]. Figure 17 As shown; and the dimensions of the five coupled nanostructures 211 contained in the coupled grating unit 21 are shown in Table 2 below.

[0118] Table 2

[0119]

[0120] In Table 2, dimension 1 represents the outer dimension of the coupled nanostructure 211, such as half of its outer radius or outer side length; dimension 2 represents the inner dimension of the coupled nanostructure 211, such as half of its inner radius or inner side length. The units for both dimensions 1 and 2 are nm. The far-field electromagnetic response of this coupled metagrating 2 can be found in [reference needed]. Figure 18 As shown; where, Figure 18 The horizontal axis represents the sine value of the far-field refraction angle, and the vertical axis represents the wavelength. This coupled meta-grating 2 can vertically emit both normally incident and visible light incident at 25°. For example, it can vertically emit normally incident ambient light and target beams incident at 25° propagated by the optical waveguide 3, thereby enabling the function of mixing virtual and real images.

[0121] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A coupling-in superlattice grating, characterized in that, The application relates to a coupling-in grating unit (10) comprising: a plurality of coupling-in grating units (10) arranged periodically; the coupling-in grating unit (10) is configured to emit a plurality of target light beams incident thereon at corresponding target diffraction orders, and the emission angles of different target light beams are the same; the target light beams are different in wavelength, and the target diffraction orders are diffraction orders at which the target light beams are regulated to be emitted by the coupling-in grating unit (10); wherein the target light beams satisfy: the product of the wavelength of each target light beam and the corresponding target diffraction order is a constant value; by regulating the target diffraction orders corresponding to different target light beams, the target light beams have the same emission angle, and the emission angle is independent of whether the wavelengths of the target light beams are the same and whether the incident angles of the target light beams are equal.

2. The in-coupling super-structure grating of claim 1, wherein, The coupling-in grating unit (10) is configured to regulate a plurality of target light beams incident thereon at the same incident angle; different target light beams correspond to different target diffraction orders.

3. The in-coupling super-structure grating of claim 2, wherein, The period length of the coupling-in grating unit (10) is such that the target light beams are inversely proportional between the wavelength and the corresponding target diffraction order.

4. The in-coupling super-structure grating of claim 1, wherein, The coupling-in grating unit (10) is configured to regulate a plurality of target light beams incident thereon at different incident angles.

5. The in-coupling super-structure grating of claim 1, wherein, The target diffraction orders include a first target diffraction order and a second target diffraction order; the first emission angles corresponding to the first target diffraction orders of different target light beams are the same, and the second emission angles corresponding to the second target diffraction orders of different target light beams are the same; the first emission angle and the second emission angle are deviated from different arrangement directions of the coupling-in grating unit (10).

6. The in-coupling super-structure grating of claim 5, wherein, The coupling-in grating unit (10) is configured to regulate a plurality of target light beams incident thereon perpendicularly.

7. The in-coupling super-structure grating of claim 1, wherein, The plurality of target light beams include a red-band light beam, a green-band light beam and a blue-band light beam.

8. The in-coupling super-structure grating of claim 1, wherein, The coupling-in grating unit (10) comprises a plurality of coupling-in nanostructures (101) arranged in a line along the shape of the coupling-in grating unit (10); at least part of the coupling-in nanostructures (101) are different in shape.

9. The in-coupling super-structure grating of claim 8, wherein, The coupling-in nanostructure (101) is a nanostructure determined by maximizing the minimum diffraction efficiency, and the minimum diffraction efficiency is the minimum value of the diffraction efficiencies of all the target light beams.

10. A coupling-out superlattice grating, characterized in that, The application relates to a coupling-out grating unit (21) comprising: a plurality of coupling-out regions (20) arranged in sequence along a preset direction, wherein the coupling-out region (20) comprises a plurality of coupling-out grating units (21) arranged along the preset direction; the coupling-out grating unit (21) is configured to couple out a plurality of target light beams incident thereon at the same incident angle; different target light beams are different in wavelength; the plurality of target light beams propagate as a whole along the preset direction, and the diffraction efficiencies of the plurality of coupling-out regions (20) arranged in sequence along the preset direction gradually increase; The diffraction efficiency of each of the out-coupling regions (20) is configured to make the light intensity distribution of the plurality of target light beams coupled out by each of the out-coupling regions (20) uniform; the diffraction efficiency of each of the out-coupling regions (20) satisfies: ; wherein, denotes the diffraction efficiency of the n-th out-coupling region (20) arranged along the predetermined direction, and N denotes the total number of the out-coupling regions (20).

11. The out-coupling superlattice grating according to claim 10, wherein, the coupling-out grating unit (21) comprises a plurality of coupling-out nanostructures (211) arranged in a line along the shape of the coupling-out grating unit (21); at least part of the coupling-out nanostructures (211) are different in shape.

12. The out-coupling superlattice grating of claim 11, wherein, The out-coupling nanostructures (211) in each of the out-coupling regions (20) are determined by maximizing an objective function that satisfies: ； wherein, denotes the diffraction efficiency of the n-th out-coupling region (20) along the predetermined direction for the i-th target light beam, denotes the diffraction light intensity of the n-th out-coupling region (20) for the i-th target light beam, denotes the reflection light intensity of the n-th out-coupling region (20) for the i-th target light beam, denotes the theoretical diffraction efficiency corresponding to the n-th out-coupling region (20), and N denotes the total number of the out-coupling regions (20).

13. An image combiner, characterized by comprising: an in-coupling element, an optical waveguide (3) and an out-coupling element; the in-coupling element is located at the in-coupling end of the optical waveguide (3), and the out-coupling element is located at the out-coupling end of the optical waveguide (3); the in-coupling element is the in-coupling metasurface grating (1) as claimed in any one of claims 1-9, and / or the out-coupling element is the out-coupling metasurface grating (2) as claimed in any one of claims 10-12; the plurality of in-coupling grating units (10) in the in-coupling metasurface grating (1) are arranged along the overall propagation direction of the light beams, and the plurality of out-coupling grating units (21) in the out-coupling metasurface grating (2) are arranged along the overall propagation direction, the overall propagation direction being the direction from the in-coupling end to the out-coupling end of the optical waveguide (3).

14. An AR optical system, characterized by, comprising the image combiner as claimed in claim 13, an image source (4) and a relay lens group (5); the image source (4) is located at the light-incident side of the in-coupling element of the image combiner, and is configured to incident imaging light beams containing at least three target light beams to the in-coupling element; the relay lens group (5) is located in the optical path between the image source (4) and the image combiner, and is configured to project the target light beams 1:1 or magnify the projection into the image combiner.

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